How to tell what is passed when no value exists

[cemox]

For this code, how do you know that null is returned if there is no value in the querystring?\[code\]HttpContext context = HttpContext.Current;string strValue = http://stackoverflow.com/questions/1833475/context.Request[name];\[/code\]I'm asking because I never know what's being returned in many cases in the .NET framework when you don't get the value expected when it does not exist.so if \[code\]context.Request[name];\[/code\] is called and the name doesn't exist in the querystring, how do you know it returns null or an empty string so that I can properly handle the case where it does not exist?